The present invention relates to wave guides such as wave guides with circular cross-section to be used for the transmission of electrical high frequency signals in the H.sub.01 mode and over long distances.
Wave guides of this type are made for example by electrolytically depositing an electrically conductive metal onto a very accurately machined mandrel having the desired contour. Another tube is provided around the tube as resulting from the electrolytic process, and the space between these tubes is filled with an electrically insulating material. A wave guide made in such a manner has a smooth inner surface, accurately dimensioned circular cross-section, and when used in straight path of conduction, this wave guide is indeed suitable for transmission of wide band H.sub.01 type waves.
It is also known to use a corrugated jacket as the outer tube, and plastic is injected into the space and cured for hardening. The wave guide proper results from galvanically depositing, e.g., copper on a cylindrically, ground steel mandrel with fine surface finish as the mandrel or die surface condition will determine the smoothness of the wave guide. The peak to valley weight of any residual surface roughness must be quite small. A wave guide made in that manner may be several meters long. The resulting wave guide, particularly when provided with a corrugated outer jacket is a satisfactory product. However, it is quite difficult to separate the tube made by the electrolytic process from the mandrel (see German printed patent application No. 1,640,739).